import java.util.Comparator;
import java.util.List;
class Card{
     int a = 10;
     int b = 20;
}
public class Test {
    public Card card2;
    public void swap(){
        Card card1 = card2;
        System.out.println(card1.a);
    }
}
   class MySingleList {
       public ListNode head;
       public ListNode last;

    static class ListNode {
        public int val;
        public ListNode next;
        public ListNode prev;
        public ListNode(int val) {
            this.val = val;
        }
    }
        public void display() {
        head.prev=last;
        last.next=head;
        System.out.println(head.val);
    }

    class IntCmp implements Comparator<Integer>{
        @Override
        public int compare(Integer o1, Integer o2) {
            return o1.compareTo(o2);
        }
    }

}








